package com.example.async.Thread;

/**
 * 使用同步机制将单例模式中的懒汉式改写线程安全
 */
public class BankTest {
}

class Bank {
    private Bank() {
    }

    private static Bank instance = null;

    public static Bank getInstance() {
        //方式一：效率稍差
//     synchronized (Bank.class){
//         if (instance == null) {
//             instance = new Bank();
//         }
//         return instance;
//     }
        //方式二：效率稍高
        if (instance == null) {
            synchronized (Bank.class) {
                if (instance == null) {
                    instance = new Bank();
                }
            }
        }
        return instance;
    }
}